The proposed research will continue studies on the genetics and biochemistry of modification of viral DNA by methylating enzymes. We have shown earlier that, by virtue of a mutational event, uPl forms of T2 gt produce an altered DNA methylating enzyme. We are concerned with being able to purify the mutant and wild-type enzymic forms and to determine if any differences exist in their size and complexity (subunits). In addition, we will examine the (partial) nucleotide sequences containing the adenines which are methylated by the two enzymic forms to determine what changes in recognition have occurred as a result of the uP1 mutation.